Lemon Balm in Zone 6A — Mountain West

Lemon Balm is a fantastic herb for Mountain West gardens. Its lemony scent and flavor are refreshing in teas, salads, and even desserts, and it's incredibly satisfying to harvest fresh leaves on a cool summer evening. Plus, it thrives in our intense sunlight and cool nights, which actually enhance its flavor.

Our high altitude, short growing season, and alkaline soil can present challenges, but Lemon Balm is surprisingly adaptable. With a little planning and attention to watering, you can easily enjoy a bountiful harvest within our 153-day growing season.

Starting Lemon Balm indoors is an option, especially if you want a head start on the season. This is a good choice if you want a more mature plant ready to go as soon as the weather warms up in our typically late spring.

Sow seeds indoors from mid-March through early April, about 6 weeks before you plan to transplant. Use seed trays with a good seed-starting mix, keep them warm (around 70°F), and provide plenty of light. Bottom watering helps prevent damping-off, a common issue with seedlings.

Transplant your Lemon Balm seedlings outdoors in early to late May, after the last expected frost. This is also about the time our risk of hail starts to pick up, so watch the forecast.

Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. Space them 18-24 inches apart in a sunny or partially shaded spot. Be sure to protect from UV when they first go out.

Direct sowing Lemon Balm is a simple and effective method, especially since it germinates readily. The downside is that you'll have a later start than if you start indoors.

Sow seeds directly into the garden from early May through early July, once the soil has warmed up to at least 60°F. Prepare the soil by loosening it and removing any weeds. Space seeds 18-24 inches apart.

Lemon Balm needs consistent moisture, but it doesn't like to be waterlogged, which is something to watch out for in our heavy alkaline soils. While some herbs are drought-tolerant, this one is not.

In the Mountain West's dry climate, water deeply about once a week, providing roughly 1 inch of water. Use the "finger test" – if the top 2 inches of soil feel dry, it's time to water. During hotter spells, you might need to water more frequently.

Water at the base of the plant to avoid wetting the foliage, as this can increase the risk of powdery mildew, even in our low-humidity environment. Signs of underwatering include wilting leaves, while overwatering can lead to yellowing leaves and root rot. A layer of mulch around the base of the plant will help retain moisture and regulate soil temperature, especially with our intense sun.

Lemon Balm requires minimal pruning, but a little attention goes a long way. This herb can get leggy if you let it.

In midsummer, cut back the plant by about half to encourage bushier growth and prevent it from becoming too leggy. Regularly remove flower stalks to prevent self-seeding, as Lemon Balm can be quite aggressive in spreading. At the end of the season, before the first frost hits around early October, give the plant a final trim.

You can start harvesting Lemon Balm leaves as soon as the plant is established, usually from early July through early October in our zone. The flavor is best before the plant starts to flower, so harvest frequently.

To harvest, simply snip off the leaves with scissors or pinch them off with your fingers. Be careful not to damage the main stem. Regular harvesting encourages continued production. As the first frost approaches in early October, harvest any remaining leaves before they are damaged by the cold.

Here are some common problems you might encounter with Lemon Balm in the Mountain West:

Aggressive Spreading

• What it looks like: Lemon Balm popping up in unwanted areas of your garden.
• What causes it: Lemon Balm readily self-seeds and spreads via underground rhizomes.
• How to fix/prevent it: Remove flower stalks before they go to seed. Consider growing Lemon Balm in containers to limit its spread.

Bolting

• What it looks like: The plant sends up a flower stalk prematurely, and the leaves become bitter or tough.
• What causes it: Bolting is often triggered by heat or drought stress, both common in our Mountain summers.
• How to fix/prevent it: Keep the soil consistently moist, especially during hot weather. Provide some afternoon shade. Harvest regularly to encourage leaf production over flowering.

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves and stems.
• What causes it: Powdery mildew thrives in warm days, cool nights, and moderate humidity, though dry leaf surfaces favor it.
• How to fix/prevent it: Improve air circulation by spacing plants adequately. Remove affected leaves promptly. Neem oil or potassium bicarbonate sprays can help.

Mountain West Specific Challenges: Our intense sun can stress Lemon Balm, leading to bolting if not properly watered. While our low humidity helps prevent many fungal diseases, powdery mildew can still be an issue. Be sure to provide consistent moisture and some afternoon shade to keep your Lemon Balm thriving.

Lemon Balm is a beneficial companion plant for several vegetables.

Good companions include tomatoes, squash, broccoli, and cauliflower. Lemon Balm repels certain pests that can harm these plants, like cabbage moths and squash bugs. It also attracts beneficial insects like bees and hoverflies, which help pollinate your vegetables.

Avoid planting Lemon Balm near other herbs that prefer drier conditions, as its moderate watering needs may create an environment that is too moist for them.